Abstract:

The methylene blue (MB) doped stearic acid composite film was deposited onto the surface of a single mode potassium ion(K⁺) exchanged glass optical waveguide (OWG) by spin coated method, the OWG sensor was fixed on the OWG sensor testing system to detect acidic gases. In the presence of hydrogen chloride (HCl) gas, the color of the MB-stearic acid composite film changed from dark blue to light blue, this led to a decrease in the evanescent absorbance of the film, increased output light intensity of the sensor. The experimental results show that the sensor has high repeatability and selectivity towards lower concentration HCl gas at room temperature, its response time and recovery time for 1×10^-6% HCl gas are 7 and 20 s, respectively, the relative standard deviation (RSD) of output light intensity is ±6.06% at this concentration. The sensor has high sensitivity, fast response and recovery speed, good reversibility, low cost and is easily fabricated.

Key words: Optical waveguide sensor, HCl gas, Spin coated method, Methylene blue-Stearic acid composite film